DOCl Dl ITM. 



Genus 10. DOCIDIUM Breb. 1844; em. Lundell, 1871. 



. in Did. uuiv. hist, nat. 1844, p. 92. 

 Lund. Dcsin. Sure. 1S71, p. *s di.'iractei-s more strictly drawn up . 



Cells straight, much elongated, more or less cylin- 

 drical, circular \vlien viewed from the apex, slightly 

 const i-ictcd in tlie middle; apices truncate and smooth; 

 base of each semicell inflated and longitudinally pli- 

 cate; one axile chloroplast in each semicell, with 

 several irregular ridges, often partially applied to the 

 cell-wall, and containing a number (about 6-8) of 

 pyrenoids disposed in a more or less median series; 

 with no conspicuous vacuole near the apex; cell-wall 

 smooth, faintly punctate, or delicately striolate. 



Much confusion has at different times existed concerning 

 the o-enera Dix-iilinni and Pleurotasnium, and they are yet 

 regarded by many authors as unworthy of separation. For 

 sonic years past we have accepted the characters of the genus 

 Dri<l in in as they were laid down by Lmiclell in 1871. The 

 L>vnus thus includes a few species which arc marked off from 

 species of the genus Pleurotsenium by very decisive char- 

 acters, the most important of which are the central or axilc 

 chloroplasts and the plication of the base of the semicells. 



The most important feature of the genus is undoubtedly 

 the ^tUccitfil baxc of the semicells accom /miiicd 1>y a f 



There are only three British species. 



1 . Dociditim Baculum Breb. 

 (PI. XXVII, figs. 1-6.) 



? Closterium Baculum Ihvb. Alg. Falaise, 1835, p. 59, t. 8. 



JJoridium Txn-uhnn lirt'b. in Diet, nniv. hist. nat. 18-14, p. 92; I'reb. in 



Ralfs' Erit. Dosm. 1848, p. 158, t. 33, f. 5; Aivh. in Priteh. Infus. ISlil, 



p. 745, t. 3, f . 38 ; Lund. Dosni. Suec. 1871, p. 88 ; Kirchn. Alg-. Schles. 



1S7S, p. 14-1; Cooke, Frit. Dcsm. 1886, p. 1(3, t. 7, f. 4 ; Hansg. 1'ro.lr. 



Al^vnll. IJdlnn. 1SSS, p. 1S8; Do Toni, Syll. Alg\ 1889, p. 872; IJori;-. 



D.'-sm. Brasil. is,! lo, p. y:53 ; West, Al\ W. Ireland, 1892, p. 117 ; Eoy 



\ IJiss. Scott. Desm. 1894, p. 241 ; West & G. S. West. Alg. Madag. 



IS'.).',, p. 11, t. 5, f. 30 ; Some N. Amer. Dosni. ls ( .i(5, p. 234, t. 12, f. :;:, ; 



Nordst. Index Desm. ]S9(>, p. 55 ; West & G. S. West, Alg. S. Enghm.l. 



1SD7, p. 482 ; Alga-fl. Yorks. 1900, p. 58 ; Alg. N. Ireland, 19<>2, p. 25: 



Freshw. Alg. Ceylon, 1902, p. 141. 



Clostt'riiiw Hfi'i>l rum Kill/. Phycol. germ. 1845, p. 133. 

 Penium BamJum Kiitz. Spec. Alg. 1849, p. Ids. 



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